In conventional tank containers, the tank is disposed within a box-like framework the end parts of which are joined to each other via a base structure and upper longitudinal beams, so that the framework completely surrounds the tank.
U.S. Pat. No. 4,593,832 discloses a tank container in which the framework is reduced substantially to two rectangular end frames which are directly joined to the tank via end mounting structures, so that considerable savings in respect of material and weight are achieved.
With smaller tanks of for instance a maximum diameter of 1800 mm, as are used also as lift-on lift-off containers for dump body systems, frame structures of the specified kind are still unnecessarily heavy.
For lifting the known tank containers by means of cable lashings, grappler arms and spreaders, it is furthermore required that all four top corner fittings of the container framework or, respectively, all four grappler arm pockets provided on the framework should be engaged by the respective hoisting equipment. This entails corresponding expenditure of labour and time in the container handling.
A tank container with the features set forth in the first part of claim 1 is known from DE-A-No. 2 532 492. In one embodiment illustrated in that document, the framework consists of a bottom structure and two end frames, each end frame including two supports slanting upwardly from the transverse beam of the bottom structure to form the shape of an equilateral triangle. In the transport and storage positions, the tank is rotated about its longitudinal axis within the framework by such an angle that the tank armatures including an upper manhole and a lower discharge funnel lie within those corners of the rectangular overall framework profile that are left free by the circular profile of the tank. This permits the tank to be made as large as possible within the available profile. Accordingly, the tank reaches the highest point of the framework profile in the transport and storage positions and extends beyond the framwork profile in the filling and discharging positions.
The considerations underlying the known tank container are based on the usual box-shaped frame having a rectangular profile even though only triangular end frames are shown in one embodiment. If these are the only framework elements, the tank armatures are unprotected in all positions. Therefore, the known container is not suited in practice for handling by a number of usual hoisting equipments.